Asthma is the most common chronic disease of childhood in the United States. Children living in poverty and in urban centers, many of whom are persons of color and are at greater risk for environmental exposures, suffer disproportionately from asthma. Many important triggers of asthma, including allergens and airborne particulate matter (PM), occur in the indoor environment. Given the complex interaction of physical and social environmental factors on childhood asthma, there have been increasing calls for comprehensive strategies using a community-based participatory research (CBPR) approach. Community Action Against Asthma is a long standing CBPR partnership in Detroit, Michigan, composed of representatives from community-based organizations, health and human service agencies and academia. This CBPR intervention is a randomized controlled trial of the efficacy of air filters (AFs) and air conditioners (ACs) to reduce indoor PM and improve health status of children with asthma above and beyond a standard community health worker home visit intervention (standard). The specific aims are to:1) test the efficacy of AFs separately and when combined with ACs to reduce exposure to indoor PM, over and above a standard intervention;2) test the association between the use of AFs separately and with ACs and the health status of children over and above a standard intervention;3) elucidate the causal pathways by which any intervention- related improvements in children's asthma-related health status occurs;4) communicate and disseminate research findings to multiple audiences;5) enhance our partnership and gain an increased understanding of factors that facilitate and impede the use of a CBPR approach to environmental health research through a process and impact evaluation. 200 households in Detroit, Ml with at least one child with persistent asthma (mild to severe) will be enrolled and will be randomly assigned to a control group (receiving the standard intervention) or the intervention group (receiving the standard intervention plus AFs initially and ACs added later). Extensive exposure and health measures will be undertaken throughout the 20 month intervention. Given the role of the indoor environment triggers in childhood asthma, there is a need to test the efficacy and efficiency of novel approaches to reducing indoor air pollutants. A CBPR approach will enhance the relevance of this research, and increase the likelihood of successfully improving the health of urban children.